Patients with gastrointestinal carcinomas are studied for evidence of reactivity against tumor-associated determinants expressed on both fresh and cultured syngeneic or allogeneic tumor cells using immunofluorescence and immunoperoxidase staining techniques. Various human malignant cell lines have been established in vitro and are being characterized morphologically and immunologically. An experimental model of pancreatic carcinoma has been developed in hamsters. Tumor-associated antigens have been isolated from both animal and human pancreatic cancers and are being investigated for possible applications to immunotherapy or methods of immunodiagnosis. Tissue-specific antigens have been isolated and are being investigated for possible use in immunotherapy of pancreatic carcinoma. Monoclonal antibodies have been developed to tumor-associated determinants in pancreatic cancers. Tolerance of normal and surgically-manipulated tissues to intra-operative radiotherapy is being investigated in dogs.